It all depends on the player behind the shield.
Yeah, uh, duh. Same goes for every class. You could hand pick several top players and use them as an example as to why X class is balanced or OP, but you'd be wrong in doing so. Likewise, you could point at a few below-average players for the same classes and make the flawed argument that the class must be weak since they're at the bottom of the scoreboard. No point in citing one specific example in a matter like this.
They are perfectly viable.
Not saying they aren't. Sure, they block projectiles, but beyond that they are pretty useless. The purpose of this post is to encourage more players to bring them along by making them more appealing to use, instead of having only one function while weakening your other combat abilities. If shields could do more than simply block ranged attacks, then we might see more people start to use them. At the very least, they shouldn't detract so much from your other abilities, such as your running speed when they aren't even in use. The objective of this thread isn't to get shields buffed, per se, but rather to give players more of a reason to bring them along and spec their builds to do so.
If you are using shields to duel, you are doing it wrong.
Agree to disagree, then. As of now shields are definitely a hindrance in duels, but there really isn't any reason why they should remain to be. It kinda hurts your argument that you point out how a player is good with shields so therefore they must be balanced, but if he sheathes his shield whenever he duels, is he really even a shielder? Or is he just a swashbuckler that hides behind a piece of wood when the arrows start raining down on him?